1. Field of the Invention
The present invention relates to the field of placement technology. More specifically, the present invention relates a placement machine and a method to control a placement machine.
2. The Prior Art
The automatic placement of electronic circuits (PCBs or similar) by means of placement machines has been known for some time and is used, in particular, whenever complex and extensive circuits are required to have a fairly laroe number of components placed on them quickly, efficiently, and without a large number of errors. The components in this process are sorted by type on individual tapes which are rolled on reels fed in steps, by means of a corresponding feeder, past a pickup position where they are picked up by a handling machine and placed in their allocated position in the circuit. In this process, the components are stored individually on the tape in pockets positioned periodically one after the other and are normally protected against falling or damage by an overlying cover tape. Such automatic placement devices are known, for example, from U.S. Pat. Nos. 4,610,083, 4,653,664, 5,191,693, 5,289,625 and 5,515,600.
Because the electronic circuits for component placement normally contain a variety of different components, and because a separate feeder is usually required on the placement machine for each component, the feeder means are designed in a space-saving manner so that the largest possible number of them can be fit next to each other on the placement machine and still be reached by the pickup head of the placement machine in a short time (see here, for example, the figures from U.S. Pat. No. 5,515,600 or FIG. 13 of European Patent Document No. A2-0 476 577). The minimum width of the feeder is determined by the width of the tape used for the components.
During the operation of such a placement machine, it frequently occurs that the stored components runout in individual feeders, or that a feeder with one component type has to be replaced with another feeder with a different component type. In order to insert new tape reels or to replace the feeder, the affected feeder must be removed by the operator. If this is done during an on-going placement process, the situation may arise where the pick-up head is just performing a pick-up process at the affected feeder or is just traveling to the feeder for the pick-up of a component while the affected feeder is being removed. In this case, a collision may occur between the pick-up head and the feeder which may damage the relatively sensitive pick-up head, as well as the feeder. Even if the motion of the pick-up head is correctly followed by the operator--which is difficult in view of the high speed of the pick-up head--incorrect placements may occur after the removal of the feeder if the pick-up head actually travels to the empty position of the removed feeder. While it is, in principle, feasible to interrupt the placement process and to stop the placement machine for each removal of a feeder in order to avoid these problems, such a procedure will lead to substantial delays in the placement procedure, which can generally not be tolerated.
It is therefore the object of the present invention to provide a placement machine and a feeder and a method for its control in which a replacement or removal of an individual feeder can be made at any time safely, in a simple way, and without any loss in performance.
It is a further object of the present invention to provide a feeder which can be taken out of the placement machine without risk and in a controlled manner during the placement procedure.
It is a further object of the present invention to provide for a pick-up process which can be aborted in a controlled manner.
It is a further object of the present invention to provide for a feeder which can be logged off at the central processing unit of the placement machine (machine computer) in a controlled manner.
It is a further object of the present invention to provide for an apparatus and process where no placement errors occur during the feeder removal from the placement machine during the placement process.
It is a further object of the present invention to provide for no loss in performance, because the placement machine can continue as a defined process in the placement program and a subsequent placement can be performed as soon as the missing feeder is replaced.
It is a further object of the present invention to provide for no occurrence of collision with the placement tool (pick-up head) when the pick process is aborted in a controlled manner.